Chlorinative dehydrogenation of hydrocarbons

ABSTRACT

Aliphatic hydrocarbons of from four to six carbon atoms are dehydrogenated by passing the hydrocarbons and chlorine through a reaction zone containing a catalyst of iron phosphates of group IIA metals, optionally promoted with a minor amount of chromia, at a temperature of from 450* to 675* C.

United States Patent Lohr, Jr. et al.

[451 Aug. 22, 1972 [54] CHLORINATIVE DEHYDROGENATION OF HYDROCARBONS [72] Inventors: Delmar Frederick Lohr, Jr., Bedford Heights; Grant Crane; Joseph A. Beckman, both of Akron,

[21] Appl. No.: 76,240

52 US. Cl. ..260/677 XA, 260/6833 [51 Int. Cl ..C07c 11 12 [58] Field of Search ..260/677 XA, 680 D, 683.3

[56] References Cited UNITED STATES PATENTS 3/1965 Carroll et a] .2607659 3,207,806 9/ l 965 Bajars .260/68 3 ,383,429 '5/ 1968 Noddings ..260/669 3,210,436 1 H1965 Bajars et al ..260/680 3,629,354 12/1971 Beard, Jr. ..260/683.3 7

Primary Examiner-Delbert E. Gantz Assistant Examiner-4. Nelson Attorney-S. M. Clark and Gordon B. Seward ABSTRACT Aliphatic hydrocarbons of from four to six carbon atoms are dehydrogenated by passing the hydrocarbons and chlorine through a reaction zone containing a catalyst of iron phosphates of group IIA metals, op-

tionally promoted with a minor amount of chromia, at a temperature of from 450 to 675 C.

8 Claims, No Drawings bons is desirably kept to a minimum.

CHLORINATIVE DEHYDROGENATION OF HYDROCARBONS BACKGROUND OF THE INVENTION This invention relates to the gas-phase dehydrogenation of hydrocarbons to the corresponding olefins, diolefins, acetylenes or triolefins.

In the production of unsaturated hydrocarbons, useful as polymerizable monomers in the manufacture of plastics and elastomers, a number of processes have been employed. One such process employs a suitable catalyst to convert a substantial proportion of a principally paraffinic feed to the corresponding monoolefins, with hydrogen as a by-product. Oxidative dehydrogenation processes utilize oxygen in the feed, and yield water vapor as a by-product. The inclusion of halogen, along with oxygen, in the feed has also been disclosed.

In all of these known processes a principal aim is to obtain as high as possible conversion of the feed material, with a maximum proportion of the effluent appearing as the desired unsaturated hydrocarbons, and a minimum amount of unwanted by-products. Thus a need exists for a system which would produce a high conversion of the saturated starting materials, with a correspondingly high selectivity to olefinic or diolefinic products. Selection of the combination of a process and a catalyst system which act together to produce optimum results is of prime importance to investigators in the field of petrochemicals.

SUMMARY OF THE INVENTION The process of the invention presents a means for dehydrogenating hydrocarbons with improved conversion and selectivity to the desired unsaturated hydrocarbons.

In essence, the invention is carried out by passing a mixture of the hydrocarbon feed, together with from 0.1 to 2.0 moles of chlorine per mole of hydrocarbon at a temperature of from about 450 to about 675? C. in contact with a catalyst of iron phosphates of group HA metals, to obtain the corresponding hydrocarbon having the same number of carbon atoms and a greater degree of unsaturation. The catalyst can optionally be promoted with minor amounts of chromia to aid in coke removal.

The hydrocarbon feed material of the invention is selected from straight chain or branched chain paraffins of from four to six carbon atoms, monoolefins or diolefins of from four to six carbon atoms, or mixtures thereof.. Examples of feed materials are n-butane, npentane, n-hexane, isobutane, methyl butane, butenel, cis-butene-Z, trans-butene-2, 2-methyl-butene-3, 2- methyl-butene-l and mixtures thereof. Refinery byproducts consisting of a mixture of four-carbon compounds are a typical feed stock.

The chlorine fed into the reaction will react primarily to give HCl, and will also produce various chlorinated hydrocarbons, to a lesser degree. The reaction is designed to produce unsaturated hydrocarbons, principally, and the production of chlorinated hydrocar- The amount of chlorine used can vary from 0.1 to 2.0 moles of chlorine per mole of hydrocarbon feed, and will preferably be from about 0.5 moles to L5 moles per mole of hydrocarbon. In general. higher ratios of chlorine will produce a greater degree of unsaturation in the products, but may also produce an increased amount of chlorinated hydrocarbons.

A diluent material can also be used such as nitrogen or steam, or both. Air may be employed as a partial source of diluent, although the process works well in the absence of oxygen. Steam is especially advantageous, as it may be easily condensed out of the product stream. From about five to about 35 moles of steam per mole of feed hydrocarbon can be used advantageously. The use of from zero to about four moles of nitrogen per mole of hydrocarbon feed may be desirable from a handling standpoint, but is not essential to the process.

The reaction zone may be of any convenient design which gives good contact between the catalyst and the gaseous mixture passing advantageously employed.

The catalyst of the invention is essentially a mixed phosphate of iron and a metal from group IIA, prepared in any convenient manner. Although the relative proportions of the metals do not appear to be critical, an atomic ratio of group IIA metal to iron ranging from 7.5 to 9.2 is found to be most effective. In general, the catalyst can be readily prepared by co-precipitating soluble iron and group IIA metal salts, washing the precipitate to remove remaining soluble materials, and drying the precipitate to constant weight. The dried catalyst can be prepared in pellet form or ground to any desired particle size for use in fixed-bed or fluid-bed reactors.

Optionally, a minor amount of chromia can be added to the catalyst before drying. It has been found that the presence of this minor amount of chromia aids in removing coke from the catalyst during the regeneration process. Regeneration is advantageously accomplished by passing air or oxygen, mixed with steam, over the catalyst at normal operating temperatures (as defined below).

In operation, the mixture of feed hydrocarbons, chlorine, and optionally diluent materials can be passed through a pre-heating manifold in which the mixture is raised to a preheat temperature of from 200 to 300 C. This step is not essential, but is helpful in that the reactants arrive at the reaction zone at a temperature close to that employed in the zone itself, and the reaction temperature can be better controlled.

The preferred temperature of the invention for the reaction zone is from about 450 C. to about 675 C., and the reactor can be jacketed to provide for heat input or removal to maintain this optimum range.

The effluent gas leaving the reaction zone is treated to separate it into its components. Water vapor is condensed out by cooling, and the unreacted chlorine and by-product HCl are recovered. The chlorine can be recycled, and the HCl can be oxidized to chlorine, which in turn can also be recycled into the reaction zone. The remaining gaseous products can be separated by fractionation if desired, or further processed in their mixed state.

The unsaturated hydrocarbon products of the invention find many uses as chemical intermediates or as polymerization monomers. By-product materials can be re-cycled, or recovered and used. The chlorinated hydrocarbons, while not the desired products of this invention, may also be used as polymerization monomers or chemical intermediates, with or without separating the mixture of chlorinated hydrocarbons into its components.

For convenience, the process can be operated at apof water and added to a mixture of 136.8 g of 85 percent phosphoric acid and 250 ml of water. To this solution was added slowly with stirring a solution of 235.8 g of calcium chloride dihydrate and 32.4 g of ferric proximately atmospheric pressure, although higher or 5 chloride in 600 ml of water, causing precipitation of the lower pressures can be employed if desired. calcium-iron phosphate. During the above addition small amounts of 30 percent aqueous ammonia were SPECIFIC ENIBODIMENTS OFTHEINVENTION added periodically in order to maintain the reaction In order to illustrate the practice of the invention the l f at P stlrfmg was fontmued 05 after following examples are supplied. Unless otherwise 10 (111110? the chlol'lde Solutions w p f T specified, all percentages and parts are by weight. precipitate was collected by filtration, re-slurried with r r water and filtered. The re-slurrying was repeated until EXAMPLE} the precipitate was free of chloride ion as determined by addition of silver nitrate solution to the filtrate. Durg g ysi t q i r of the mventlon was ing the final re-slurrying 4.4 g of chromium oxide was pr are 1 e o wmg added to the slurry. The catalyst filter cake was air Two hundred a i li gz g 5: El dried overnight and then dried to constant weight in an 3 32 i W d 85 O g; oven at 140 C. The length of the drying period is not an a a mlx re 0 g o perce, critical. Weight of the dried catalyst was 129.8 g. The; PhOSPhOYIC and 400 ml 9 lce al ld water T thls quantities of reagents used were chosen to give an sohmon was adfled Slowly Stlmng a Sohmon of atomic CazFe ratio of 8.2. The catalyst was ground as in 325 g of magnesium chloride hexahydrate and 32.4 g of Example L ferric chloride in 400 ml of water, causing precipitation EXAMPLE III of the magnesium-iron phosphate. During the above addition small amounts of 30 percent aqueous amt f f gzi z i ig i g g i zg fi. were added pemdicany in Order maintain the isdll ih a fixgd 1225:1511 bed as 51611 a s with reaction mixture at pH 8. Stirring was continued 0.5 hr. an reactor Anal Sis of the rociuct was made after addition of the chloride solutions was complete. g line hronzlato a h ,F incomin ases The precipitate was collected by filtration, re-slurn'ed t 56 and the g was with water and filtered. The re-slurrying was repeated l gl g f 0 r m re of about 550 C until the precipitate was free of chloride ion as determam m a an age e P u throughout the trials. Proportions of the varlous incomminecl by addition of silver mtrate solution to the fil m d l trate. During the final re-slurrying 3.8 g of chromium mg e uent gases. a f gaseolllls oxide was added to the slurry. The filter cake was air hour"), Space velocmes (G 6 me as t e volumes of material passed through the reactor (cordried overnight and then dried to constant weight m an 5 rected to standard temperature and pressure) per hour, oven at 140 C. Weight of the dried catalyst was 166.0 (lid d b the volume of the reactor The differin g. The quantities of reagents used were chosen to give e y h f l an atomic Mg Fe ratio of 8 2 The catalyst was ground GHSV s reflect t e use 0 l erent reactor vo umes, to a article z of 10 zo'n'tesh the flow of the feed hydrocarbon material (butane) was p essentially the same in all runs. Pressure in the reactor EXAMPLE n 40 was atmospheric, or slightly above. Measurements are summarized in the following table, showing improved In a similar manner as Exam le 1, a second catalyst selectivit to butenes and butadiene (BD), and reduced p a n l y 0 I was prepared. Two hundred and fifty-eight milllhters of amounts of chlorinated products with the catalysts of 30 percent aqueous ammonia were diluted with 250 ml the invention. 1

G.H.S.V Selectivity Run No. Butane Air N2 012 Steam g); Butenes BD Total 131213);

ily??? 52 11s 52 1,050 82 51 12 53 High, 51 11s 03 1,030 59 42 15 51 High. 49 130 52 910 s0 5 12 58 High.

01 200 15 1,500 14 54 2a 11 Low. 12 200 140 1, 590 81 45 a1 10 Low.

12 215 52 2,015 52 01 2a 54 Low. 14 215 50 2,125 15 55 2s 84 Low. 215 2,250 84 49 s2 81 Low. 14 215 2,110 92 39 31 10 Low. 54 250 25 52 2,050 55 41 20 01 Low. 11 250 25 80 1,995 51 40 21 51 Low. 11 250 25 91 2,290 55 a9 21 55 Low. 12 250 25 115 2,210 94 30 32 52 Low.

15 215 02 2, 030 59 02 20 82 Low. 15 215 80 2,150 12 55 20 84 Low. 14 215 91 2,100 53 50 20 10 Low. 14 215 115 2, 255 04 40 a1 11 Low. 13 25 02 2,110 05 40 2a 03 Low. 14 25 50 2,100 83 40 21 01 Low. 74 25 97 2,160 J1 35 2!) (54 Low. 76 26 116 2,120 .15 31 38 67 Low.

6 We claim: 4. The process of claim 1, wherein the group [IA 1. A process for dehydrogenating aliphatic hydrocarmetal is magnesium. I bons of from four to six carbon atoms which comprises 5 The process of claim 1, wherein the aliphatic contacting a mixture of the hydrocarbons and chlorine hydrocarbons consi t tially f b ta or with a catalyst of iron phosphates of group HA metals 5 tanes.

wherein the atomic ratio of group lIAmetals to iron in 6. The process of claim 1, wherein the molar ratio of said catalyst is from 7.5 to 9.2 atoms of group HA chlorine to hydrocarbons is from 0.1 to 2.0 moles of metals per atom of iron at a temperature of from 450 chlorine per mole of hydrocarbons.

to 675 C. 7. The process of claim 1, wherein an inert diluent is 2. The process of claim 1, wherein the catalyst is 10 added to the mixture of chlorine and hydrocarbons.

promoted with a minor amount of chromia. 8. The process of claim 3, wherein the inert diluent is 3. The process of claim 1, wherein the group HA steam, or nitrogen, or mixtures of these materials.

metal iS calcium.

UNETED STATES PATENT OFFICE CERTIFICATE OF CGRRECTION Patent No. 3, 3 +5 Dated August 7 Inventor) Qelmar Frederick Lohr, Jr. Grant Crane and aosepn A. becxman It; is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

{- Cols. 3 and in the Table at the bottom of the page, I

Ru'n -"7, under the heading "Conversion" "'75" should read --76..

Run No. 8, under the heading "C1 "95" should'read ---97-- C01. 6, claim 8, change "3" to --7-- Signed and sealed this 9th day of January 1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK 1 Attesting Officer Commissioner of Patents 5 

2. The process of claim 1, wherein the catalyst is promoted with a minor amount of chromia.
 3. The process of claim 1, wherein the group IIA metal is calcium.
 4. The process of claim 1, wherein the group IIA metal is magnesium.
 5. The process of claim 1, wherein the aliphatic hydrocarbons consist essentially of butanes or pentanes.
 6. The process of claim 1, wherein the molar ratio of chlorine to hydrocarbons is from 0.1 to 2.0 moles of chlorine per mole of hydrocarbons.
 7. The process of claim 1, wherein an inert diluent is added to the mixture of chlorine and hydrocarbons.
 8. The process of claim 3, wherein the inert diluent is steam, or nitrogen, or mixtures of these materials. 